Sure, but at the moment i still have an error when sending bigger files(50kb). Then im getting a resend request send back after the 131.packet of 195. Any idea how i should react to that, or why the error might be happening?Is something wrong with my checksum calculation, or the way im processing the bytes?

Maybe do you have to skip the extra '\' bytes when calculating the checksum, or do you have to ignore them in the size send of the package? It seems wrong and the other way its working for small files, so i really dont know why it isnt working for big files.